Composite materials such as engineered stone, which is a composite material made from crushed stone that is bound together by an adhesive such as polymer resin, are gaining popularity for making various household articles and fixtures, including sinks and countertops. One common stone used for producing engineered stone sinks and other household fixtures is quartz. Related materials include geopolymers and cast stone. Unlike other materials, some items made from engineered stone such as sinks are molded to produce a desired shape and surface finish or texture. When molding an engineered-stone sink, an uncured mixture of stone and binder are placed in a closed mold to cure. Upon curing, the now solid article is removed from the mold and subjected to finishing operations such as trimming, machining, polishing and the like.
Typical sink molds are made of two pieces, a lower mold and an upper mold. The lower mold typically shapes the exterior of the sink, and also any other sink features such as an apron. The upper mold shapes the interior of the sink and, usually, a top flange surface used to mount the sink to the underside of a countertop. To allow extraction of the cured sink from the lower mold, and also the upper mold, draft angles are designed in connection with the various sink surfaces and edges. The draft angles, which are typical for molded articles, can range between 0.5 and 5 degrees, depending on the size and shape of the molded features and the surface texture of the various faces, especially the surfaces extending along a mold separation direction. While the draft angles are necessary, they affect the shape of the sink, which can detract from its aesthetics in certain applications.